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By means of molecular imprinting of a conducting polymer, molecular cavities selective for oxytocin nonapeptide, an autism biomarker, were designed. Embedding of the oxytocin template, and then its extracting from the molecularly imprinted polymer (MIP) was confirmed by the XPS analysis. AFM imaging of the MIP film surface indicated changes in mechanical properties of the film after template extraction. The MIP synthetic receptor was deposited by potentiodynamic electropolymerization as a thin film on an Au film electrode in an electrochemical miniaturized microfluidic cell. The use of this cell allowed to shorten analysis time and to decrease the sample volume. The linear dynamic concentration range extended from 0.06 to 1 mM with the limit of detection of 60 µM (S/N = 3). Advantageously, sensitivity of the diagnostic microfluidic platform devised for oxytocin determination in both synthetic serum samples and in aqueous solutions was similar and, moreover, it was selective to common interferences, such as oxytocin analogs and potential metabolites. [ABSTRACT FROM AUTHOR]

A molecularly imprinted polymer (MIP)-based chemosensor for the selective determination of a chosen toxin, N-nitroso- l-proline (Pro-NO), was devised and fabricated. By means of DFT, the structure of the pre-polymerization (functional monomer)-template complex was modeled. This complex was then potentiodynamically electropolymerized in the presence of cross-linking monomer to form a MIP-Pro-NO thin film. Next, the Pro-NO template was extracted from MIP-Pro-NO with 0.1 m NaOH. Piezoelectric microgravimetry (PM) on an electrochemical quartz crystal microbalance and electrochemical (differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS)) techniques were used to transduce binding of Pro-NO to molecular cavities of the MIP-Pro-NO. With DPV and EIS chemosensing, the limits of detection (LODs) were about 80.9 and 36.9 nM Pro-NO, respectively; and the selectivity coefficients for urea, glucose, creatinine, and adrenalin interferences were 6.6, 13.2, 2.1, and 2.0, respectively, with DPV as well as 2.3, 2.0, 3.3, and 2.5, respectively, with EIS. With PM under flow injection analysis conditions, the LOD was 10 μ m Pro-NO. The MIP-Pro-NO chemosensor detectability and selectivity with respect to interferences were sufficiently high to determine Pro-NO in protein-providing food products. [ABSTRACT FROM AUTHOR]

An elevated concentration of d -arabitol in urine, especially compared to that of l -arabitol or creatinine, is indicative of a fungal infection. For that purpose, we devised, fabricated, and tested chemical sensors determining d -arabitol. These chemosensors comprised the quartz crystal resonator (QCR) or extended-gate field-effect transistor (EG-FET) transducers integrated with molecularly imprinted polymer (MIP) film recognition units. To this end, we successfully applied a covalent approach to molecular imprinting, which involved formation of weak reversible covalent bonds between vicinal hydroxyl groups of arabitol and boronic acid substituents of the bithiophene functional monomer used. The MIP films were synthesized and simultaneously deposited on gold electrodes of quartz crystal resonators (Au-QCRs) or Au-glass slides by oxidative potentiodynamic electropolymerization. With the QCR and EG-FET chemosensors, the d -arabitol concentration was determined under flow-injection analysis and stagnant-solution binding conditions, respectively. Selectivity with respect to common interferences, and l -arabitol in particular, of the devised chemosensors was superior. Limits of detection and linear dynamic concentration ranges of the QCR and EG-FET chemosensors were 0.15 mM and 0.15 to 1.25 mM as well as 0.12 mM and 0.12 to 1.00 mM, respectively, being lower than the d -arabitol concentrations in urine of patients with invasive candidiasis (>220 μM). Therefore, the devised chemosensors are suitable for early diagnosis of fungal infections caused by Candida sp. yeasts. [ABSTRACT FROM AUTHOR]

With an established procedure of molecular imprinting, a synthetic polymer receptor for the neopterin cancer biomarker was devised and used as a recognition unit of a potentiometric chemosensor. For that, bis -bithiophene derivatized with cytosine and bithiophene derivatized with boronic acid were used as functional monomers. The open-circuit potential (OCP) based transduction under flow-injection analysis conditions (FIA) determined neopterin in the concentration range of 0.15–2.5 mM with the 22 µM limit of detection (LOD) and 7.01(±0.15) mV mM −1 sensitivity indicating its potential suitability in clinical analysis applications. The molecularly imprinted polymer (MIP) film showed an appreciable apparent imprinting factor of ~6. The chemosensor successfully discriminated the interferences including the 6-biopterin and pterin structural analogs of neopterin as well as glucose and creatinine. Moreover, it determined neopterin in synthetic serum samples. [ABSTRACT FROM AUTHOR]

The present review article focuses on gathering, summarizing, and critically evaluating the results of the last decade on separating and sensing macromolecular compounds and microorganisms with the use of molecularly imprinted polymer (MIP) synthetic receptors. Macromolecules play an important role in biology and are termed that way to contrast them from micromolecules. The former are large and complex molecules with relatively high molecular weights. The article mainly considers chemical sensing of deoxyribonucleic acids (DNAs), proteins and protein fragments as well as sugars and oligosaccharides. Moreover, it briefly discusses fabrication of chemosensors for determination of bacteria and viruses that can ultimately be considered as extremely large macromolecules. [ABSTRACT FROM AUTHOR]

Receptors found in natural living systems specifically recognize target biomolecules. If applied to biosensing, they offer the much desired high selectivity. However, their instability under measurement conditions and low durability prompted researchers toward devising different artificial receptor alternatives. For instance, an antibody is successfully mimicked by a corresponding molecularly imprinted polymer (MIP), sometimes called a plastic antibody. Nowadays, MIPs are widely used as recognition units in chemical sensors. The present mini review critically surveys selected recent representative examples of MIPs, and functionalized monomers used to devise these MIPs for the determination of biologically important target analytes by mimicking their natural recognition routes. [ABSTRACT FROM AUTHOR]

Highlights: [•] New trends in chemosensing using molecularly imprinted polymers (MIPs). [•] Importance of the control over the ratio of surface area to volume. [•] Preparation of MIPs with the high (surface area)-to-volume ratio. [•] Analytical parameters of MIP chemosensors. [ABSTRACT FROM AUTHOR]

Abstract: Environmental and health safety requires thorough determination of hazardous compounds and drugs of abuse. In determinations of these analytes, traditional instrumental analytical techniques often suffer from tedious assay procedures. Biosensors are simpler to construct and faster in use, so they can better meet the analytical demands in determination of these biohazards. However, their stability and reproducibility when operating under harsh conditions are poor, so artificial recognition units have become attractive as replacements for natural receptors in sensing applications. Molecular imprinting is one of the most powerful tools for preparing materials that can bind analytes reversibly and selectively in the presence of their interferents. This review critically evaluates the development of chemical sensing of biohazards and drugs of abuse using the molecular-imprinting approach to recognition in combination with different ways of analytical signal transduction. We compile analytical parameters of the molecularly-imprinted receptors, identify difficulties in the determinations encountered and highlight proposed solutions to problems. [Copyright &y& Elsevier]

Abstract: Zwitterionic molecularly imprinted polymeric chains were tethered to the sol–gel modified graphite electrode in brush pattern of high density, for the quantitative estimation of creatine at trace level, without any cross reactivity, in real samples. The modified electrode was activated by preanodization at +1.4V (vs. saturated calomel electrode) for the fast ion-exchange recapture of creatine, under mild basic condition (pH 7.1). The detection limit was as low as 1.3µgmL−1 (signal/noise=3) employing differential pulse, cathodic stripping technique. [Copyright &y& Elsevier]

Abstract: A voltammetric sensor based on a molecularly imprinted polymer (MIP) brush grafted to sol–gel film on graphite electrode is reported for the selective and sensitive analysis of barbituric acid (BA) in aqueous, blood plasma, and urine samples. The modified electrode was preanodised at +1.6V (vs. saturated calomel electrode), where encapsulated BA involved hydrophobically induced hydrogen bondings, in MIP cavities exposed at the film/solution interface, at pH 7.0. Scanning electron microscopy (SEM) was employed to characterise the surface morphology of the resultant imprinted film of MIP brush. The differential pulse, cathodic stripping voltammetry (DPCSV) technique was employed to investigate the binding performance of the sol–gel-modified imprinted polymer brush, which yielded a linear response in the range of 4.95–100.00μgmL−1 of BA with a detection limit of 1.6μgmL−1 (S/N =3). [Copyright &y& Elsevier]

Abstract: The development of an easy-to-use, rapid, robust and inexpensive technique is required which can measure the basal concentration of uric acid (UA) lower than 1.0×10−7 M (∼0.017mgL−1) in biological samples to attend the problem of hypouricemia. In the present work an artificial receptor for UA, silica gel-bonded molecularly imprinted polymer (MIP), was used as a sorbent for molecularly imprinted solid-phase extraction (MISPE) in column chromatography. The use of a sensor based on a MIP-modified hanging mercury drop electrode (HMDE), as reported from our laboratory, could estimate UA with detection limit as low as 0.024mgL−1 under the optimized conditions of differential pulse, cathodic stripping voltammetric (DPCSV) measurement. However, in the current investigation, with the use of the combination of MISPE followed by detection with a MIP-based HMDE sensor, the minimum detectable concentration could go down to 0.0008mgL−1 (RSD=0.63%, S/N=3). The same MIP receptor for both MISPE and the corresponding sensor was able to enhance the preconcentration of analyte substantially so as to attain the desired level of sensitivity; and that to without any interference (cross-reactivity) from other structurally related analogues including the major interferent like ascorbic acid prevalent in the aqueous environment of biological samples. [Copyright &y& Elsevier]

In the global market era, food product control is very challenging. It is impossible to track and control all production and delivery chains not only for regular customers but also for the State Sanitary Inspections. Certified laboratories currently use accurate food safety and quality inspection methods. However, these methods are very laborious and costly. The present review highlights the need to develop fast, robust, and cost-effective analytical assays to determine food contamination. Application of the molecularly imprinted polymers (MIPs) as selective recognition units for chemosensors' fabrication was herein explored. MIPs enable fast and inexpensive electrochemical and optical transduction, significantly improving detectability, sensitivity, and selectivity. MIPs compromise durability of synthetic materials with a high affinity to target analytes and selectivity of molecular recognition. Imprinted molecular cavities, present in MIPs structure, are complementary to the target analyte molecules in terms of size, shape, and location of recognizing sites. They perfectly mimic natural molecular recognition. The present review article critically covers MIPs' applications in selective assays for a wide range of food products. Moreover, numerous potential applications of MIPs in the food industry, including sample pretreatment before analysis, removal of contaminants, or extraction of high-value ingredients, are discussed. [ABSTRACT FROM AUTHOR]

Molecular recognition, i.e., ability of one molecule to recognize another through weak bonding interactions, is one of the bases of life. It is often implemented to sensing systems of high merits. Preferential recognition of the analyte (guest) by the receptor (host) induces changes in physicochemical properties of the sensing system. These changes are measured by using suitable signal transducers. Because of possibility of miniaturization, fast response, and high sensitivity, field-effect transistors (FETs) are more frequently being used for that purpose. A FET combined with a biological material offers the potential to overcome many challenges approached in sensing. However, low stability of biological materials under measurement conditions is a serious problem. To circumvent this problem, synthetic receptors were integrated with the gate surface of FETs to provide robust performance. In the present critical review, the approach utilized to devise chemosensors integrating synthetic receptors and FET transduction is discussed in detail. The progress in this field was summarized and important outcome was provided. [ABSTRACT FROM AUTHOR]

Nanostructured artificial receptor materials with unprecedented hierarchical structure for determination of human serum albumin (HSA) are designed and fabricated. For that purpose a new hierarchical template is prepared. This template allowed for simultaneous structural control of the deposited molecularly imprinted polymer (MIP) film on three length scales. A colloidal crystal templating with optimized electrochemical polymerization of 2,3′-bithiophene enables deposition of an MIP film in the form of an inverse opal. Thickness of the deposited polymer film is precisely controlled with the number of current oscillations during potentiostatic deposition of the imprinted poly(2,3′-bithiophene) film. Prior immobilization of HSA on the colloidal crystal allows formation of molecularly imprinted cavities exclusively on the internal surface of the pores. Furthermore, all binding sites are located on the surface of the imprinted cavities at locations corresponding to positions of functional groups present on the surface of HSA molecules due to prior derivatization of HSA molecules with appropriate functional monomers. This synergistic strategy results in a material with superior recognition performance. Integration of the MIP film as a recognition unit with a sensitive extended-gate field-effect transistor (EG-FET) transducer leads to highly selective HSA determination in the femtomolar concentration range. [ABSTRACT FROM AUTHOR]

A novel recognition unit of chemical sensor for selective determination of the inosine, renal disfunction biomarker, was devised and prepared. For that purpose, inosine-templated molecularly imprinted polymer (MIP) film was deposited on an extended-gate field-effect transistor (EG-FET) signal transducing unit. The MIP film was prepared by electrochemical polymerization of bis(bithiophene) derivatives bearing cytosine and boronic acid substituents, in the presence of the inosine template and a thiophene cross-linker. After MIP film deposition, the template was removed, and was confirmed by UV–visible spectroscopy. Subsequently, the film composition was characterized by spectroscopic techniques, and its morphology and thickness were determined by AFM. The finally MIP film-coated extended-gate field-effect transistor (EG-FET) was used for signal transduction. This combination is not widely studied in the literature, despite the fact that it allows for facile integration of electrodeposited MIP film with FET transducer. The linear dynamic concentration range of the chemosensor was 0.5–50 μM with inosine detectability of 0.62 μM. The obtained detectability compares well to the levels of the inosine in body fluids which are in the range 0–2.9 µM for patients with diagnosed diabetic nephropathy, gout or hyperuricemia, and can reach 25 µM in certain cases. The imprinting factor for inosine, determined from piezomicrogravimetric experiments with use of the MIP film-coated quartz crystal resonator, was found to be 5.5. Higher selectivity for inosine with respect to common interferents was also achieved with the present molecularly engineered sensing element. The obtained analytical parameters of the devised chemosensor allow for its use for practical sample measurements. [ABSTRACT FROM AUTHOR]

• A rapid method was developed for determining MMP-1 and SP-A biomarkers predictive for idiopathic pulmonary fibrosis. • Chemosensors were devised, fabricated, and tested for selective determination of the biomarkers. • Films of polymers molecularly imprinted with biomarkers' epitopes constituted chemosensors' recognition units. • The films were deposited by electropolymerization on gates of extended-gate field-effect transistors used as signal transducers. • The LOD was as low as to enable the procedure to be suitable for selective biomarkers' determination in body fluids. We propose a relatively rapid and straightforward procedure for the determination of chosen idiopathic pulmonary fibrosis (IPF) predictive protein biomarkers, vis., matrix metalloproteinase-1 (MMP-1) and surfactant-associated protein-A (SP-A), suitable for their determination in bodily fluids. IPF is a lethal lung disease, annually causing nearly as many deaths as breast cancer. Moreover, the coronavirus recently triggered acute exacerbation of patients suffering from IPF. Here, epitopes specific to the chosen IPF biomarkers were molecularly imprinted in a polymer as an alternative to imprinting fragile whole biomarkers' molecules. A thin molecularly imprinted polymer (MIP) film-based recognition units were integrated by electropolymerization with gates of extended-gate field-effect transistors (EG-FETs) to fabricate biomarker-selective chemical sensors suitable as point-of-care testing (POCT) diagnostic devices. Either AQDDIDGIQAI or FKGNKYWAVQGQNV single-epitope imprinting allowed determining the MMP-1 biomarker in the 10 to 250 nM linear dynamic concentration range with a LOD of 7.5 or 2 nM, respectively. Simultaneous imprinting of three MMP-1 epitopes, vis., MIAHDFPGIGHK, HGYPKDIYSS, and FKGNKYWAVQGQNV, decreased this LOD to 0.1 nM, allowing for determining this biomarker in serum. Moreover, by FSSNGQSIT or YSDGTPVNYTNWYR single-epitope imprinting, chemosensors for SP-A were fabricated to show the versatility of epitope imprinting. These chemosensors selectively determined the SP-A biomarker with the LOD of 1.9 or 2.9 nM, allowing its determination in bodily fluids. [Display omitted] [ABSTRACT FROM AUTHOR]

We fabricated an electrochemical molecularly imprinted polymer (MIP) chemosensor for rapid identification and quantification of E. coli strain using 2-aminophenyl boronic acid as the functional monomer. This strain is a modified Gram-negative strain of Escherichia coli bacterium, an ordinary human gut component. The E. coli strongly interacts with a boronic acid because of porous and flexible polymers of the cell wall. The SEM imaging showed that the bacteria template was partially entrapped within the polymeric matrix in a single step. Moreover, this imaging confirmed E. coli K-12 cell template extraction effectiveness. The prepared MIP determined the E. coli K-12 strain up to 2.9 × 104 cells mL−1. The interference study performed in the presence of E. coli variants expressing different surface appendages (type 1 fimbriae or Antigen 43 protein) or Shewanella oneidensis MR1 , another Gram-negative bacteria, demonstrated that the bacterial surface composition notably impacts sensing properties of the bacteria imprinted polymer. [Display omitted] • E. coli E2152 was successfully imprinted in a polymer by 2-aminophenylboronic acid and aniline co-electropolymerization. • The bacteria template was entrapped in the resulting molecularly imprinted polymer in a single step. • Thus prepared MIP film-based electrochemical chemosensor determined E. coli E2152 up to 2.9 × 104 cells/mL. • E. coli E2152 determination was selective versus bacteria of other surface properties. [ABSTRACT FROM AUTHOR]

Abstract: Molecularly imprinted polymers (MIP) have been elucidated to work as artificial receptors. In our present study, a MIP was applied as a molecular recognition element to a chemical sensor. We have constructed a creatinine sensor based on a MIP layer selective for creatinine and its differential pulse, cathodic stripping voltammetric detection (DPCSV) on a hanging mercury drop electrode (HMDE). The creatinine sensor was fabricated by the drop coating of dimethylformamide (DMF) solution of a creatinine-imprinted polymer onto the surface of HMDE. The modified-HMDE, preanodised in neutral medium at +0.4V versus Ag/AgCl for 120s, exhibited a marked enhancement in DPCSV current in comparison to the less anodised (≤+0.3V) HMDE. The creatinine was preconcentrated and instantaneously oxidised in MIP layer giving DPCSV response in the concentration range of 0.0025–84.0μgmL−1 [detection limit (3σ) 1.49ngmL−1]. The sensor was found to be highly selective for creatinine without any response of interferents viz., NaCl, urea, creatine, glucose, phenylalanine, tyrosine, histidine and cytosine. The non-imprinted polymer-modified electrode did not show linear response to creatinine. The imprinting factor as high as 9.4 implies that the imprinted polymer exclusively acts as a recognition element of creatinine sensor. The proposed procedure can be used to determine creatinine in human blood serum without any preliminary treatment of the sample in an accurate, rapid and simple way. [Copyright &y& Elsevier]

Redox - active molecularly imprinted polymer nanoparticles selective for glyphosate, MIP-Gly NPs , were devised, synthesized, and subsequently integrated onto platinum screen-printed electrodes (Pt-SPEs) to fabricate a chemosensor for selective determination of glyphosate (Gly) without the need for redox probe in the test solution. That was because, ferrocenylmethyl methacrylate was added to the polymerization mixtures during the NPs synthesis so that the resulting MIP-Gly NPs contained covalently immobilized ferrocenyl moieties as the reporting redox ingredient, conferring these NPs with electroactive properties. MIP-Gly NPs of four different compositions were evaluated. The herein described approach represents a simple and effective way to endow MIP NPs with electrochemical reporting capabilities with neither the need to functionalize them post-synthesis nor to use electrochemical mediators present in the tested solution during the analyte determinations. MIP-Gly NPs synthesized using allylamine and squaramide-based monomers appeared most selective to Gly. The Pt-SPEs modified with MIP-Gly NPs were characterized with differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Changes in the DPV peak originating from the oxidation of the ferrocenyl moieties in these MIP-Gly NPs served as the analytical signal. The DPV limit of detection and the linear dynamic concentration range for Gly were 3.7 pM and 25 pM–500 pM, respectively. Moreover, the selectivity of the fabricated chemosensors was sufficiently high to determine Gly successfully in spiked river water samples. [Display omitted] [ABSTRACT FROM AUTHOR]

Herein, electrochemically active molecularly imprinted polypyrrole nanoparticles (PPy NPs) were synthesized with the aid of micelles. Iron(III) p -toluenesulfonate induced polymerization of pyrrole resulting in the imprinting of estriol in growing NPs. Two separate imprinted NPs were prepared with pristine and derivatized pyrrole monomers. Techniques such as scanning electron microscopy (SEM), and transmission electron microscopy (TEM), confirmed the synthesis of imprinted PPy NPs of ∼60 nm in size. NPs prepared with pristine pyrrole showed an imprinting factor of 4.2, while NPs prepared with derivatized pyrrole showed no imprinting. The electrochemical-based transduction allowed for the determination of estriol in the concentration range of 0.5–5 µM and 10–100 µM with the 0.16 µM limit of detection (LOD). Furthermore, the selectivity of the MIP NP-coated electrode toward estriol and its structural analogs, namely β-estradiol and estrone, was satisfactory. [Display omitted] • Molecularly imprinted polypyrrole nanoparticles were synthesized with the aid of micelles. • Electrochemically active molecularly imprinted polypyrrole nanoparticles were applied in the chemosesnsing of estriol. • Better chemosensing performance of imprinted nanoparticles was observed for nanoparticles prepared with pristine pyrrole. • High selectivity of imprinted nanoparticles toward estriol compared to its structural analogs was confirmed. [ABSTRACT FROM AUTHOR]

A conducting molecularly imprinted polymer (MIP) film was integrated with an extended-gate field-effect transistor (EG-FET) transducer to determine epitopes of matrix metalloproteinase-1 (MMP-1) protein biomarker of idiopathic pulmonary fibrosis (IPF) selectively. Most suitable epitopes for imprinting were selected with Basic Local Alignment Search Tool software. From a pool of MMP-1 epitopes, the two, i.e., MIAHDFPGIGHK and HGYPKDIYSS, the relatively short ones, most promising for MMP-1 determination, were selected, mainly considering their advantageous outermost location in the protein molecule and stability against aggregation. MIPs templated with selected epitopes of the MMP-1 protein were successfully prepared by potentiodynamic electropolymerization and simultaneously deposited as thin films on electrodes. The chemosensors, constructed of MIP films integrated with EG-FET, proved useful in determining these epitopes even in a medium as complex as a control serum. The limit of detection for the MIAHDFPGIGHK and HGYPKDIYSS epitope was ∼60 and 20 nM, respectively. Moreover, the chemosensors selectively recognized whole MMP-1 protein in the 50–500 nM concentration range in buffered control serum samples. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Two selective chemosensors for adenosine-5′-triphosphate (ATP) determination featuring molecularly imprinted polymer (MIP) film recognition units were fabricated. For imprinting, three different thiophene derivatives were used as functional monomers. That is, the uracil substituent of bis(2,2′-bithienyl)methane 2 complementarily H-bond paired the adenine moiety of ATP, the boronic acid substituent of thiophene 3 covalently bound vicinal diols of the ribofuranose moiety, and amide substituents of bis(2,2′-bithienyl)methanes 4 bound to the pyrophosphate moieties. Different binding motifs adopted for the ATP recognition and the structure of the supramolecular pre-polymerization complex were optimized with the DFT computing at the B3LYP/3-21G(⁎) level. MIP films were prepared by potentiodynamic electropolymerization of this complex with the imprinting factor of 9.47±0.2. An analytical signal was transduced with a 10-MHz resonator of EQCM and a Pt electrode for the piezoelectric microgravimetry (PM) and capacitive impedometry (CI) determination of ATP, respectively, under FIA conditions. Analytical properties of the MIP film were unraveled by spectroscopic ellipsometry, XPS, IRRAS, and DPV. The limit of detection was 0.1 and 0.2μM for the PM and CI chemosensor, respectively, being an order of magnitude lower than the ATP concentration in biological systems. Moreover, cross-selectivity was demonstrated with the adenosine-5′-diphosphate (ADP) imprinting and ATP discrimination. [Copyright &y& Elsevier]

Abstract: Highly efficient enantioselective separation and quantitative recoveries of d- and l-tryptophan in aqueous and real samples can be achieved, with a monolithic molecularly imprinted polymeric fiber that serves both for micro-solid phase extraction and ultratrace sensing, without any false-positive (non-specific) contribution and cross-reactivity, in the range of 0.15–30.00ngmL−1 with detection limit as low as 0.0261ngmL−1 (relative standard deviation=0.64%, signal/noise=3). The proposed method combining molecularly imprinted micro-solid phase extraction fiber and a complementary molecularly imprinted polymer–carbon composite fiber sensor is proven to be useful for clinical diagnosis of stress-related diseases caused by acute tryptophan depletion. [Copyright &y& Elsevier]

Abstract: An insulin-imprinted polymer was synthesized over the surface of vinyl group functionalized multiwalled carbon nanotubes, using phosphotidylcholine-containing functional monomer and cross-linker. Phosphotidylcholine is a major component of all biological membrane; its incorporation in polymer backbone assures water-compatibility, bio-compatibility and specificity to molecularly imprinted nanomaterials, without any cross-reactivity or interferences from biological sample matrices. An electrochemical sensor fabricated by modifying multiwalled carbon nanotubes-molecularly imprinted polymer onto the pencil graphite electrode, was used for trace level detection of insulin in aqueous, blood serum, and pharmaceutical samples (detection limit 0.0186nmolL−1, S/N=3), by differential pulse anodic stripping voltammetry. Additional cyclic voltammetry (stripping mode) and chronocoulometry experiments were performed to explore electrodics and kinetics of electro-oxidation of insulin. [Copyright &y& Elsevier]

Abstract: The present work describes a new, simple, and easy method for the generation of stable molecularly imprinted sites in polymeric film, combining self-assembled monolayer and Layer-by-layer approaches through thermal cross-linking of the layered structures, onto the surface of silver electrode. Modified silver electrodes demonstrate enantiodifferentiation and sensitive (detection limits 0.0060ngmL−1 for l- and 0.0062 for d-thyroxine) determination of d- and l-thyroxine with the help of differential pulse anodic stripping voltammetric technique. The binding kinetics of thyroxine was explored using anodic stripping cyclic voltammetry and chronocoulometry. The sensor was also validated for d- and l-thyroxine determinations in biological and pharmaceutical samples. [ABSTRACT FROM AUTHOR]

Abstract: Thyroxine is a known disease biomarker which demands a highly sensitive and selective technique to measure ultratrace level with enantiodifferentiation of its optical isomers (d- and l-), in real samples. In this work, an approach of hyphenation between molecularly imprinted micro-solid phase extraction and a complementary molecularly imprinted polymer-sensor was adopted for enantioseparation, preconcentration, and analysis of d- and l-thyroxine. In both techniques, the same imprinted polymer, coated on a vinyl functionalized self-assembled monolayer modified silver wire, was used as the respective extraction fiber as well as sensor material. This combination enabled enhanced preconcentration of test analyte substantially so as to achieve the stringent limit [limit of detection: 0.0084ngmL−1, RSD=0.81%, S/N =3 (d-thyroxine); 0.0087ngmL−1, RSD=0.63%, S/N =3 (l-thyroxine)] of clinical detection of thyroid-related diseases, without any problems of non-specific false-positive contribution and cross-reactivity. [Copyright &y& Elsevier]

Abstract: Molecularly imprinted polymers (MIPs) are often electrically insulating materials. Due to the presence of diffusion barrier(s) in between such MIP coating and electrode surface and the absence of a direct path for the conduction of electrons from the binding sites to the electrode, the development of electrochemical sensor is significantly restricted. The direct use of MIPs those possess intrinsic electron-transport properties, is highly limited. These problems are resolved by the design of an original, substrate-selective MIP-fiber sensor that combines conventional insulating MIP and conducting carbon powder in consolidated phase. A layer of conducting carbon particles, arranged orderly as ‘carbon strip’, is inducted in the polymer for direct electronic conduction. MIP–carbon composite (monolithic fiber) in this work is prepared via in situ free radical polymerization of a new monomer (2,4,6-trisacrylamido-1,3,5-triazine, TAT) and subsequent cross-linkage with ethylene glycol dimethacrylate, in the presence of carbon powder and template (folic acid), at 55°C in a glass capillary. The detection of folic acid with the MIP-fiber sensor was found to be specific and quantitative (detection limit 0.20ngmL−1, RSD=1.3%, S/N=3), in aqueous, blood serum and pharmaceutical samples, without any problem of non-specific false-positive contribution and cross-reactivity. [Copyright &y& Elsevier]

Abstract: Electrochemical sensors demonstrating enantioselectivity to tryptophan enantiomers, with high selectivity and sensitivity, were fabricated by the use of a monolithic fiber of molecularly imprinted polymer-carbon composite. The recognition mechanism and performance of these sensors were evaluated by differential pulse anodic stripping voltammetry. The sensor imprinted for l-tryptophan not only discriminated the target from its analogues and other amino acids but also responded specifically in racemic mixture in aqueous, biological, and pharmaceutical samples. The binding kinetics of l-tryptophan was also established with the help of anodic stripping cyclic voltammetry and chronocoulometry. The detection limit for l-tryptophan was as low as 0.24ngmL−1 (signal/noise=3) which is appropriate for biomarking diseases, caused by an acute tryptophan-depletion, in clinical setting. [Copyright &y& Elsevier]

Abstract: Contrary to the ‘substructure imprinting approach’ of larger molecule like folic acid, which often leads molecular recognition for both folic acid and structural analogues containing pteridine and glutamic acid substructures, a molecularly imprinted polymer capable of binding specifically folic acid has been prepared by stoichiometric imprinting process (template/monomer molar ratio, 1:3) creating multiple binding sites within the cross-linked hyperbranched polymer. Dendrimer-like chains were obtained by an ‘initiator-fragment incorporation radical polymerization’ technique involving a new trifunctional monomer, 2,4,6-trisacrylamido-1,3,5-triazine. An electrochemical sensor was developed for the selective and quantitative recognition of folic acid, using a preanodized sol–gel coated pencil graphite (grade 2B) electrode with imprinted polymer immobilized to its exterior surface. During preconcentration step at +0.8V (with respect to Ag/AgCl), the analyte recapture at pH 2.5 in aqueous environment simultaneously involved mixed hydrophobically driven hydrogen bondings and ionic interactions with pteridine substructure and purely hydrogen bonding interactions with glutamic acid residue of folic acid. The encapsulated analyte was instantly oxidized and then cathodically stripped off responding differential pulse cathodic stripping voltammetric signal. The folic acid was selectively detected with a limit of detection of 0.002μgmL−1(3σ, RSD ≤3.0%), without any cross-reactivities and real matrix complications. [Copyright &y& Elsevier]

Abstract: A simple polymerization strategy is reported in this work which allows molecularly imprinted polymeric fiber (monolith) fabrication for direct use in sensing devices. This is advantageous for achieving higher degree of enrichment of target analyte (folic acid) from the complex matrices of real samples, without any surface fouling, cross-reactivity, and non-specific (false-positive) contributions. In order to measure serum folic acid at ultratrace level to detect spina bifida, a neural tube defect in mother, and other acute cases of proteomic diseases, the hyphenation between molecularly imprinted micro-solid phase extraction fiber and a complementary molecularly imprinted polymer–carbon composite fiber sensor has been found quite efficient. The primitive diagnosis of many chronic diseases is feasible by estimating folic acid as biomarker, with the detection limit as low as 0.0036ngmL−1 (relative standard deviation=0.13%, signal/noise=3) in human blood serum. [Copyright &y& Elsevier]

Abstract: Induced-fit responsive dopamine (DA) imprinted polymer, poly (melamine-co-chloranil), was used as a suitable coating material for the modification of a hanging mercury drop electrode. The zwitterionic conformation of the imprinted polymer responded differential pulse, cathodic stripping voltammetric current, without any false-positive or false-negative contributions of non-specific sorptions, in aqueous environment of complex matrices. The limit of detection (3σ) of dopamine was found to be as low as 0.148ngmL−1, by the proposed sensor that could be considered a sensitive marker of dopamine depletion in Parkinson''s disease (PD). [Copyright &y& Elsevier]

Molecularly imprinted polymer (MIP) nanoparticles-based differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) chemosensors for antiplatelet drug substance, cilostazol (CIL), and its pharmacologically active primary metabolite, 3,4-dehydrocilostazol (dhCIL), selective determination in human plasma were devised, prepared, and tested. Molecular mechanics (MM), molecular dynamics (MD), and density functional theory (DFT) simulations provided the optimum structure and predicted the stability of the pre-polymerization complex of the CIL template with the chosen functional acrylic monomers. Moreover, they accounted for the MIP selectivity manifested by the molecularly imprinted cavity with the CIL molecule complex stability higher than that for each interference. On this basis, a fast and reliable method for determining both compounds was developed to meet an essential requirement concerning the personalized drug dosage adjustment. The limit of detection (LOD) at the signal-to-noise ratio of S/N = 3 in DPV and EIS determinations using the ferrocene redox probe in a "gate effect" mode was 93.5 (±2.2) and 86.5 (±4.6) nM CIL , respectively, and the linear dynamic concentration range extended from 134 nM to 2.58 μM in both techniques. The chemosensor was highly selective to common biological interferences, including cholesterol and glucose, and less selective to structurally similar dehydroaripiprazole. Advantageously, it responded to dhCIL , thus allowing for the determination of CIL and dhCIL together. The EIS chemosensor appeared slightly superior to the DPV chemosensor concerning its selectivity to interferences. The CIL DPV sorption data were fitted with Langmuir, Freundlich, and Langmuir-Freundlich isotherms. The determined sorption parameters indicated that the imprinted cavities were relatively homogeneous and efficiently interacted with the CIL molecule. • Cilostazol (CIL) neuroprotective drug molecularly imprinted in polymer nanoparticles. • nanoMIP imprinted cavity design and sorption analysis with computational modeling. • nanoMIPs DPV and EIS chemosensors for CIL and its active primary metabolite. • The 134 nM to 2.58 μM CIL concentration range and 93.5 nM (DPV) and 86.5 nM (EIS) LOD. [ABSTRACT FROM AUTHOR]

[Display omitted] • Redox self-reporting MIP film was proposed. • A bis- (2,2′-bithienyl)-4-ferrocenylphenyl methane was designed and synthesized. • Even 40% of the ferrocene moieties participated in the sensor's response. • It was necessary to copolymerize the sulfonyl acid moiety containing monomer. • The deposited MIP film thickness and morphology were crucial for sensor performance. Simultaneously, the p -synephrine 1 template was imprinted, and a ferrocene redox probe was covalently immobilized in a (bis -bithiophene)-based polymer, and the resulting molecularly imprinted polymer (MIP) was deposited on the Pt electrode as a thin film to form a redox self-reporting MIP film-based chemosensor. After subsequent template extraction from the film, analyte 1 was determined with differential pulse voltammetry (DPV) in a (redox probe)-free solution. That was possible because the internal ferrocene redox probe generated the DPV analytical signal. The thickness and morphology of the film were crucial for the sensor's performance. The self-reporting mechanism was examined with electrochemical techniques, simultaneous piezomicrogravimetry and electrochemistry at an electrochemical quartz crystal microbalance, and surface plasmon resonance spectroscopy. The chemosensor was applied for selective p -synephrine determination in a concentration range of 2.0–75 nM with the LOD of 0.57 nM at S / N = 3. [ABSTRACT FROM AUTHOR]

Abstract: Clinical manifestations owing to ascorbic acid deficiency demand an easy-to-use, rapid, robust and inexpensive technique, which can measure serum ascorbic acid at ultratrace level to attend the problem of hypovitaminosis C and acute cases of scurvy. In the present work, a novel molecularly imprinted polymer (MIP)-coated solid-phase microextraction (SPME) fiber that could be coupled to a complementary MIP-sensor was prepared with ascorbic acid as a template molecule. The characteristics and applications of this fiber were investigated. The same MIP receptor for both SPME and the corresponding sensor was able to enhance the preconcentration of analyte substantially so as to attain the stringent level of sensitivity in highly diluted aqueous, blood serum and pharmaceutical samples. The extraction yield of ascorbic acid (AA) with the MIP-coated fiber was found to be quantitative (detection limit 0.0396ngmL−1, RSD=2.3%, S/N=3) in aqueous samples without any problem of non-specific false positive results and cross-reactivity. [Copyright &y& Elsevier]

• Impedance measurements can be used for fast and continuous evaluation of the gasoline aging. • Electrical parameters of the fuel decrease importantly with the aging time. • The observed changes indicate formation of polar and/or ionic products. • The EIS conclusions are supported by observed spectral changes in aged gasoline. Fuels stored in storage tanks undergo aging processes. In particular, this applies to fuels containing biocomponents. The ability to quickly assess changes taking place in fuel is more and more critical due to the growing resources of fuels stored for a long time. Moreover, it is essential for maintaining the fuel quality. The purpose of this work was to develop a method enabling determination of the stability of gasolines containing biocomponents and allowing for early warning of quality deterioration. For that, the electrochemical impedance spectroscopy (EIS) was tested as it allows for fast, easy, and continuous determination of the gasoline quality. For that, the gasoline electrical parameters were determined by the EIS before and during aging. Then those results were compared with such physico-chemical parameters that change the most quickly during aging. It has been found that selected electrical parameters derived from the impedance spectra, namely, resistance, capacitance, relaxation time, and impedance values at a given frequency decrease with the aging time linearly or exponentially. The changes of those parameters indicate the formation of polar and/or ionic products and decrease of the fuel viscosity, increasing its conductivity. Furthermore, spectral studies of the samples indicate the formation of unsaturated and aromatic hydrocarbons, as well as –OH and C=O group-containing species. These observations are corroborating well with conclusions derived from the EIS studies. Notably, the obtained results indicate the correlation between electrical parameters and critical physicochemical properties of the fuel, thus suggesting possibility of applying the electrical parameters for gasoline quality assessment. [ABSTRACT FROM AUTHOR]

• For controlled co-polymerization molar ratio of monomers of low and high oxidation potential in solution is optimized. • Co-polymerization at lower oxidation potential suppresses electrode reaction of electroactive template. • Imprinting of an electroactive analyte in electropolymerizable functional monomers is performed. • Fabricated imprinted polymer based electrochemical chemosensor shows high selectivity. Herein, we report an electrochemically initiated co-polymerization of two electroactive monomers of different oxidation potentials. The molar ratio of low oxidation potential monomer in the solution for electropolymerization was optimized to find condition suitable for co-polymerization of high-oxidation potential monomer effectively at lower oxidation potential. The XPS analysis confirmed successful co-polymerization. This co-polymerization condition was further used in imprinting of melatonin, an electroactive compound. Entrapment of melatonin in the polymer matrix was confirmed by measuring electroactivity of melatonin in the 0.1 M KCl−HCl solution (pH 1.6). This MIP based electrochemical sensor determined melatonin in the linear dynamic concentration range 10–80 μM. Detectability of proposed chemosensor was 0.14 μM (S/N = 3). The mean RSD for the concentration range studied was ∼20%. Selectivity of the chemosensor was satisfactory towards common structural analogues and biomolecules. Furthermore, the chemosensor was successfully used to determine melatonin in real samples. The sensitivity in the presence of matrix components and that for the KCl−HCl solution were quite similar. The results obtained indicate the suitability of the devised chemosensor for practical applications. [ABSTRACT FROM AUTHOR]